The invention concerns crystalline 5R,6S-6-(1-R-hydroxyethyl)-2-(N,N-dimethylamidinomethylthio)-carbapen-2-em -3-carboxylic acid, also referred to herein as dimethyliminothienamycin.
Dimethyliminothienamycin has the formula ##STR2##
It is a broad spectrum antibiotic of the carbapenem class. Its preparation (and use) in non-crystalline form is described in EUROPEAN PATENT APPLICATION No. 81-108 420,1.
A crystalline form of I has been prepared. Crystalline I is more stable than the non-crystalline form while retaining the antibiotic activity.